The drawstring footbox doesn't give me any problem. Just make a casing at the end of the bag and thread a drawsting (or elastis cord) through it. About 18" of velcro(the nonsnag stuff is nice, but weaker and needs a snap at the top)on each edge of the bottom closes the footbox.
I haven't made a baffled footbox, but I think if you study the directions carefully it will finally make sense. And if you have any trouble, Ayce will help you. Get some cheap sale fabric or muslin and make a practice quilt shell to get the hang of how it goes together, and make sure it's the right size for you.
On footbox size; if you have really big feet, make sure the width of the foot end of the quilt is enough to go around your feet when comfortably splayed. Oh, also if you use a drawsting at the bottom, make sure the quilt is long enough to go from your heal, over the bottoms of your feet and up over your shoulders.
I hope this helps.